I posted a question today about ReactOS, and discovered there's no tag for it yet. I did a search, but only a couple pages of results came up for ReactOS so it's not a popular topic at this point in time.
When it comes to tag creation there seems to be 2 approaches:
Unless there are lots of questions don't worry about it, because we can manually retro-actively apply them if a need for the tag creation ever arises.
Create it, it helps recruit experts, and saves work down the road; it's not like we can't just delete it later.
I understand the logic of both, they both have their merits, and I think they apply best to different types of tags. For example if you go with option one and create a tag for everything that ever gets asked about, things become too spread out, and the tags become useless. However if you always go with option 2 it creates extra work, and prevents addition of potentially useful tags.
In this case we're talking about an operating system tag, and not even a specific release of the operating system, just a generic tag. Tags for every OS under the sun aren't needed, case and point being the linux and windows which work generically to prevent tags for every obscure possibility. However ReactOS doesn't fit into those categories so I think it deserves a tag, even if there are very few questions for it at the moment.
If you read this post, and don't weigh in, somewhere in the world a puppy dies. :(